1. Field of the Invention
This invention relates generally to metal-clad or metal enclosed switchgear and more particularly to shutter mechanisms for switchgear apparatus having circuit interrupters or circuit breakers of the drawout type disposed in metal housings or cubicles.
2. Description of the Prior Art
In the construction of switchgear equipment of the drawout type, the primary movable disconnecting contacts of a circuit interrupter or circuit breaker are often mounted on insulating bushings which are inserted into a plurality of pairs of insulating tubes which are mounted in the associated switchgear housing to engage stationary disconnecting contacts disposed in the insulating tubes. In order to protect operating and maintenance personnel who may have occasion to enter the switchgear housing a shutter means which is usually formed from sheet metal or insulating material has been employed in the past to automatically close the openings to the insulating tubes when the associated circuit breaker is removed from its normal operating position. This shutter, generally, is activated by the breaker moving in and out of the switchgear compartment. As the breaker moves into the cell to be connected into the line, the shutter moves to a position either above or below the fixed electrical contacts. As the required voltage and current ratings of the circuit breakers employed in switchgear apparatus increase in newer applications, it became necessary to provide more efficient and effective shutter designs that maintain a sufficient distance away from any live parts to prevent the possibilities of arcing and to insure the associated apparatus would pass BIL (impulse) testing.